Vacuum heating system



Jan. 1, 1935 0. N. CROSTHWAIT: J,R 1,986,391,

I VACUUM HEATING SYSTEM Filed May 5; 1929 N hi N Patented Jan. 1, 1935UNITED STATES 1,986,391 VACUUM IIEATING SYSTEM David N. Crosthwait, Jr.,Marshalltown, Iowa,

assignor to C. A. Dunham Company, Marshalltown, Iowa,,a corporation ofIowa Application May 3, 1929, Serial No. 360,212

16 Claims.

This system relates to an improved vacuum steam heating system, and moreparticularly to a system adapted to operate with steam at controlledsub-atmospheric pressures, as disclosed 5 in the patent to Dunham1,644,114 granted tober 4, 1927.

In a system of this type, steam is supplied under a vacuum, or at asub-atmospheric pressure, to an evacuated condensing space or radiator.If there 0 are a plurality of such radiators, theproportionate volumesof steam delivered to the radiators are controlled in accordance withthe radiating capacity of each radiator and the distance of theseradiators from the source of supply. A reducing valve, thermostaticallyoperated valve, pr generator-control mechanism is provided forregulating the sub-atmospheric pressure of the steam in the radiator orradiators.

consequently the amount of heat given out by the radiator. A return mainfor withdrawing air and condensate from the radiator leads through athermostatically controlled steam trap which prevents the escape ofsteam from the radiator. An exhausting mechanism operates on the returnmain to withdraw condensate and maintain the vacuum in. the system. Adifierential pressure controller connected between the supply and returnsides of the system governs the operation of the exhausting means so asto maintain a substantially constantand predetermined difference inpressure between the supply and exhaust sides of the radiator, no matterwhat the absolute pressure of the steam in the radiator may be.

In heating buildings in many sections of the country, provision must bemade to care for sudden and severe wind conditions. For example, incertain localities there are times when high winds accompanied byfalling temperatures come from the north. In such instances, the northside of a building is hard to heat, whereas the other sides may beheated with.relative ease. In order to combat this condition, it hasbeen proposed to have separate and distinct heating systems for thedifierent portions of a building so that steam at a higher pressure andtemperature can be supplied to the heating system in that portion of abuildingsubjected to the more severe weather, conditions, while lowerpressure steam can be. supplied to the system or systems in thoseportions of the building Where less heat is required. However, in manyinstances the cost resulting from the duplication or multiplication ofparts makes this method of procedure prohibitive.

The general object of this invention is to provide an. improved vacuumheating system of this type involving two or more separate and distinctradiating or condensing systems for diiierent The pressure of the steamdetermines its temperature, and

parts of the building, all of the systems being supplied from, the samesource of steam, and a single exhausting mechanism being utilized tomaintain the requisite subatmospheric pressures throughout the variousparts of the heating system. The present invention relatesto certainimprovements in the system disclosed and claimed broadly in applicantscopending application Serial No. 285,885, .filed June 16, 1928.

A particular object of the present invention is to provide means wherebythe condensate withdrawn from the radiating system operating at thehigher pressure is revaporized, and the resultant steam utilized forheating purposes in the system operatingat the lower pressure.

Another object is to provide means whereby the steam or other gaseswithdrawn from the higher pressure system. may be discharged either intothe supply or return mains of the system operating at the lowerpressure.

' Another object is to greatly simplify the piping connections by theuse of electric control circuits. Another object is to provide anapparatus of this sort, in which either of the constituent radiatingsystems can be operated at the higher or the lower pressure, as desired,or both systems can be operated at the same sub-atmospheric pressure asa single unit.

Numerous other objects and advantages of this system will be apparentfrom the following detailed description of one approved form ofapparatus suitable for carrying out the principles of this invention. 7

In the accompanying drawing:

Fig. 1 is a diagrammatic elevation showing the principal features of theentire heating apparatus.

Fig. 2 is a detail elevation, partially in vertical section, of one ofthe radiator inlet valves and inlet orifices.

The drawing illustrates an example of an apparatus including twoseparate radiating systems adapted to operate simultaneously atdifierent sub-atmospheric pressures, although it will be apparent as thedescription progresses that more than two such systems could be operatedin the same manner. Several portions of the apparatus are common to thetwo heating systems, principal among which are the generator A, theexhausting mechanism indicated generally at B, the flash tank C, theaccumulator tank D, the driving motor E for the exhausting mechanism,the electrically operated cut-off valve F controlling the exhaust outletfrom the flash tank C, and the switch mechanism G for reversing theelectrical control circuits. There are also numerous auxiliaryconnections between these several parts, as hereinafter described.

The generator or boiler A which may be of any approved form, furnishessteam to header 1,

from which a drip pipe 2 leads back to the lower portion of the boilerat 3. A normally closed drain connection for the system is indicated at4.

The exhausting mechanism B is substantially the same as that disclosedin the Dunham patent, hereinabove referred to. A centrifugal pump 5directly coupled with and driven by the motor E withdraws water throughpipe 6 from the lower portion of tank 7 and projects this water upwardlythrough the ejector 8, discharge manifold 9 and pipe 10 back into theupper portion of the tank 7. A partial vacuum is created by the liquidstream within the ejector casing, and the air and condensate withdrawnfrom the radiating systems through pipe 11 and one-way check valve 12are entrained within the liquid stream and delivered into tank '7. Theair escapes through pipe. 13 and outwardly opening check valv'e**14.Since condensate is continually delivered to tank 7, the water levelwithin this tank will gradually rise and when a certain level is reachedthe float 15, through lever and link connections 16; will open the valve17, whereupon the pump 5 will force'water from the tank 7 through pipe18, cheok'valve 19 and normally open cut-oh valve 20, into drip pipe 2and thence back into the generator A. When the water level within tank 7has been suiilciently lowered the valve 1'7 will be closed by thedownward movement of float 15.

*' The condensate and gases withdrawn from the two radiating systemspass from the return mains of these systems (hereinafter described)-tank D when the systems are operating at or above atmospheric pressure.Normally, however, the air vent 24 will be closed since a partial vacuumwill exist in the accumulator tank D and pipe 23. r A' branch pipe 23leads to a pressure gauge which may be located in a convenient positionon the tank 7.

The motor Eis controlled from starter 25, connected through leads 26 and26' with the motor. The power lines running to starter 25 are indicatedat 27 and 28. The wires 29 and 30 of a control circuit 'lead fromstarter 25 to the various control switches hereinafter described. Anormally closed switch 31 may be connected in circuit with one of thewires 29 or 30, this switch being opened by a pressure operatedcontroller 32 connected by pipe 33 with the exhaust pipe 11 whena'certain desired maximum vacuum has been attained in the main exhaustpipe 11.

A normally open switch 34 connected by leads '35 and 36 with the starter25 is adapted to'be closed by a float mechanism 37 positioned inaccumulator tank D in case the liquid in said tank rises above apredetermined maximum level. As a result the pumping. mechanism. will bestarted to withdraw this condensate from tank D, regardless of thepressure conditions existing in other portions of the system.

Steam is delivered from the header 1 through the separate supply mains Hand H to the two radiating systems. The principal elements of each ofthese systems are substantially identical and comprise a main cut-oilvalve J, a reducing valve K, a plurality'of radiating units L, a returnmain M, a differential pressure controller N, and

other auxiliary elements and connections, as hereinafter described. Theelementsof the radiating system at the right hand side of Fig. 1 areindicated by unprimed reference characters, whereas the similar elementsof the radiating system at theleft of Fig. 1 are indicated by similarprimed reference characters. As here shown, the right hand systemcomprises two radiators "L, whereas the left hand system has only asingle radiator L, but it is to be understood that the number ofradiators in each system could be increased as found necessary ordesirable.

The several elements of one of the radiating systemswill nowbedescribed. The cut-oil valve J is normally open when the system is inoperation. The reducing valve K may be of a well known form, such asdisclosed in the Dunham patent hereinabove referred to.

the flow of steam at boiler pressure in the high pressure portion 39 ofsupply main H into the low pressure portion 40 of this supplymain. Thevalves in casing 38 are controlled through stem 41 from a diaphragmlocated in casing 42, this diaphragm being subject on one side toatmospheric pressure, and on the other side to the sub-atmosphericpressure existing in the portion 40 of the supply main H, this pressurebeing delivered through conduit 43 which connects with supply main H atsome little distance from the valves so as not to beinfluenced by thefluctuations in pressure within the .valve chamber. A lever 44 fulcrumedat 45 and pivoted at 46 to operating stem 41, supports from its ends theadjustable weights 4'7 and 48. By properly ad justing these weights, aforce is exerted through lever 44 on stem 41, which either assists oropposes the pressure differential exerted on the diaphragm in casing 42.The resultant force applied to stem 41 either opens or closes thevalves. The weights 4'7 and 48 are so adjusted that when the admissionof steam has built up the pressure to the desired vacuum orsub-atmospheric pressure in the portion 40 of supply main H,the-diaphragm in casing 42 will be moved to close the valves and shutoff the flow of further steam into the supply main from header 1. As thesteam in supply main H is condensed or otherwise dissipated, thepressure in the supply main will be lowered, so that a higher degree ofvacuum than is desired will be attained, whereupon the diaphragm will beactuated in the opposite direction to open the valves in casing 38 andadmit more steam to the supply main H. This action will be substantiallycontinuous so that the steam in portion 40 of supply main H (andconsequently in radiators L, as will be hereinafter ap- It comprises apair of balanced valves in the casing 38 for controlling parent) can bemaintained substantially constant at any sub-atmospheric pressure,regardless of the pressure of the steam supplied from generator Athrough header 1.

This steam at'sub-atmospheric pressure is'delivered from supply main Hthrough a steam riser '49 and a normally open inlet valve 50 to eachradiator L. As indicated in Fig. 2, an orifice .plate 51' is interposedin the conduit connection assess:

dividual radiator and the position of this radiator in the heatingsystem.

A steam trap 53 is interposed between the lower portion of each radiatorL and a pipe 54 leading to the return main M. When steam from theradiator enters the steam trap 53 it will expand the operating meanswithin this trap and close the valve to prevent the escape of steam intothe return main. When suiiicient condensate or air has accumulated, thevalve operating means will be cooled and will contract to open the valveand permit the escape of the condensate and air through pipe 54 into thereturn main M and thence into the exhausting mechanism. The condensatewhich accumulates in supply main H is delivered through pipe connection55, float and thermostatic trap 56 and outlet 'pipe 57 into the returnmain M. Return main M leads down through a cut-off valve 58 into pipe 59and thence through valve 21 and suction strainer 22 into accumulatortank D, as already described. A drain connection 60 provided with valve61 leads downwardly from pipe 59 to permit both of the return mains tobe drained if found to be desirable. Valve 61 is normally closed.

Alternative pipe connections 62 and 63 lead through cut-off valve 64into pipe 65 and thence into the flash tank C. It will be apparent thatwhen valve 64 is closed and valve 58 opened, the

contents of return main M will be drawn directly into the accumulatortank D. On the other hand, when valve 58 is closed and valve 64 isopened, the condensate and air in return main M will be deliveredthrough the alternative pipe connections 62. 63 and 65 into the flashtank C.

The flash tank C is provided for the purpose of permitting thecondensate returning from the radiating system that is operating at thehigher pressure to revaporize as a result of expanding to the pressureexisting in the exhausting apparatus, or in the radiatingsystem-operating at the higher vacuum or lower pressure. Such condensateas does not vaporize and accumulates in flash tank C drains through pipe66, float trap 67 and outlet pipe 68 into the exhaust pipe 11 and isthence drawn into the exhausting mechanism B. The float trap 67 preventsany steam from being withdrawn from flash tank C through the outlet pipe66. An equalizing pipe 69 extending from the upper portion of tank C tothe float trap 67 permits the ready entrance of condensate intothe trap67.

An exhaust pipe 70 leads from the upper portion of flash tank C, and inthis pipe are positioned the outwardly opening check valve 71, and

the electrically operated cut-01f valve F. This valve F may be of anysuitable type, but is preferably a solenoid operated valve that isnormally closed but which is opened when the solenoid is energized.Branch pipes 72 and 72' provided with cut-off valves 73 and 73' leadfrom pipe 70 to the respective supply mains H and H. Alternative branchpipe connections 74 and 74 lead through cut off valves 75, 75' and steamtraps 76, 76' into the pipes 62,62 and thence into the respective returnmains M and M. Normally both cut-oil? valves 75 and 75' will be closed,and one of the cut-off valves 73 or 73 will be closed, so that only oneof the branch pipes 72 or 72', the one leading to the radiating systemoperating at the lower sub-atmospheric pressure, will remain open. Ifthe difference in pressure existing between the two radiating systems isinsuflicient to vaporize a material quantity of the condensate deliveredinto flash tank C, it may be found desirable to close both cut-on valves73, 73' and open one of the cut-oil? valves 75, 75 so that the exhaustconnection from flash tank C will lead into the return main of theradiating system operating at the lower pressure. When connected in thismanner, the steam trap 76 or 76' will prevent any steam that may beformed in flash tank C from flowing out into the return main M, or M, asthe case may be. Pipe 100 leading from exhaust pipe 70 to float trap101, and drain pipe 102 leading from this trap to tank C, serve toreturn condensate accumulating in the exhaust pipe connections lastdescribed back into flash tank C.

An equalizing connection comprising the pipes 77, 78 and 79 extends fromreturn main M to supply main H in each of the two radiating systems. Inthe horizontal pipe 78 are positioned a pair of surge chambers 80 and81, a normally open cut-oil valve 82, and a one-way check valve 83opening toward the supply side of the system. Under normal conditionsthe equalizing connection will be closed by check valve 83, but if forany reason the pressure in the supply side of the system should fallbelow that in the return side, this check valve 83 will open so as topermit an equalization of the pressures. This will prevent air orcondensate from being held in the radiators or drawn back into thesupply side of the system. Control pipes 84 and 85 connect therespective chambers 80 and 81 with the two sides of thedifferential-pressure controller N. This controller .may be the same asthat disclosed in the Dunham patent above referred to, or in thecopending application of McMurrin, Serial No. 174,994, filed March 12,1927. In general, this controller comprises a casing divided into twochambers by a flexible diaphragm. The two chambers are connectedrespectively with the supply and return sides of one of the heatingsystems by the pipe connections 85 and 84, hereinabove referred to. Aspring tends to urge the diaphragm in one direction, the action of thespring being balanced by the desired pressure differential between thesupply and return sides of the system. When the pressure differentialfalls below the desired minimum, the spring will actuate the diaphragmand a stem projecting therefrom in one direction, thereby closing anormally open switch, indicated diagrammatically at 86. This switchwill, through circuits hereinafter described, affect the energizetion ofeither the motor E or the solenoid valve F. When the desired pressuredifferential has again been attained, the diaphragm will overcome thespring and open the switch 86, whereupon motor E is temporarily stopped,or valve F temporariiy closed.

a The control switch mechanism G consists of a plurality of double-throwswitches, one for-each branch or zone of the heating system. In thepresent example, there are a pair of similar double throw switches 87and 87'. The switch 86 of differential controller N is connected byleads 88 and 89 with the central pair of contacts of switch 87. In anexactly similar manner, the switch 86 of the other differentialcontroller N is connected by leads 88' and 89 with the central contactsof switch 87'. The control wires 29 and 30 extending from motor starter25 lead to one pair of end contacts of switch 87, and a pair of similarbranch wires 90 and 91 extend from wires 29 and 30 to the end contactsof switch 87'. The circuit consisting of wires 92, 93 and 94 connectsthe solenoid valve F and the other-pair of end contacts of switch 87 inseries with a source of ferred to.

power, and branch wires 95 and 96 extending in parallel from wires 93and 94 similarly connect the other pair of end contacts of switch 8'7 inthis circuit. It will now be apparent that when double throw switch 87is closed in one direction, the switch 86 of difierential controller Nwill be placed in control of the motor E of the exhausting mechanismthrough starter 25, and. when switch 8'7 is closed in the otherdirection, this differential controlled switch will be placed in controlof the solenoid valve F. In an exactly similar manner by closing theother switch 87' in one direction or the other, the differentiallycontrolled switch 86 of the other radiating system may be alternativelyplaced in control of either the motor E or the solenoid valve F. Innormal operation, one of the switches 87, 8'7 will be closed in onedirection, and the other switch in the other direction, according towhich of the two radiating systems is operating at the lower pressure orhigher vacuum.

Another equalizing connection consisting of the pipe 97 with the one-waycheck valve 98 opening toward the generator, and also provided with thenormally open stop valve 99, may be positioned between the dischargepipe 59 at the lower ends of return mains M and M and the pipe 18leading back to the generator. This equalizing connection functions thesame as the equalizing connections previously described in theindividual radiating systems.

I will first assume that one of the radiating systerms (in the examplehere shown, the one at the right hand side of Fig. 1) is to be operatedat a much lower temperature than the other radiating system, andconsequently the lower pressure (or higher vacuum) is to be maintainedin this system. In this event, the switch 87 is closed to the right toplace differential controller N in control of the motor E, and switch8'7 is closed to the left to place differential controller N of the lefthand system in control of the solenoid valve F. Cut-off valve 58 is openand cut-01f valve 64 closed so that return main M will discharge intoaccumulator tank D and thence into the exhausting mechanism B. Cut-offvalve 58 is closed and cut-off valve64 opened so that return main M willdischarge into the flash tank C. Valves '73, '75 and '75 are closed andvalve 73 is opened so that the exhaust pipe connection '70 leading fromflash tank C will be placed in communication with the supply main H ofthe lower pressure system whenever the solenoid valve F is opened. Thereducing valves K and K must be respectively adjusted so as to supplysteam at the desired 10w sub-atmospheric pressure to the right handsystem and at a somewhat higher sub-atmospheric pressure to the lefthand system.

The lower pressure or higher vacuum system at the right will now operateexactly the same as the usual differential pressure vacuum system asdisclosed in the Dunham patent hereinabove re- The propersub-atmospheric pressure of the steam in the radiators L is determinedby the adjustment of the reducing valve K, and the I exhaustingmechanism B will operate intermittently to maintain the desired vacuumin the system and also to maintain the necessary pressure differentialbetween the supply and return sides of the system. The air andcondensate are drawn directly through return main M into the accumulatortank D and thence into the exhausting mechanism B, the air beingdischarged through vent pipe 13 and the condensate returned atinter-Jails to the boiler A through pipe 18.

In the other system (designated by the primed reference characters) lessvacuum is required, since this system is to be operated with steam at ahigher pressure, since more heat is to be radiated. Accordingly, thereducing valve K is so adjusted that supply main H will furnish steam tothe radiators L at a higher sub-atmospheric pressure. The condensate andair from this system are discharged from return main M, through pipeconnections 62, 63, and 65 into the flash tank C. The pressure in theflash tank C determines the pressure in the return side of this latterradiating system. Whenever the pressure differential in this left-handsystem falls below the desired minimum, differential controller N willclose switch 86, and through the circuits already described, thesolenoid valve F will be opened so as to temporarily place flash tank Cin communication with the supply main H, wherein a considerably lowerpressure exists. The lowering of the pressure in flash tank C will causethe condensate therein (or a portion thereof) to be re-vaporized and theresultant steam will be drawn out through pipes '70 and '72 into thesupply main H of the lower pressure system, wherein the steam isutilized for heating purposes. The lowering of the pressure in flashtank C will, through return main M, again establish the necessarypressure differential in the left hand radiating system, whereuponswitch 86 will be opened and the solenoid valve F will close, so as tocut off the exhausting connections to flash tank C. Any excesscondensate in flash tank will drain out through float trap 6'7 and bedelivered into the exhaust pipe 11 and thence into the exhaustingmechanism B, from which it is returned to the generator A in the usualmanner.

We now believe it will be quite apparent that -by suitably reversing thepositions and adjustments of the several valves and switches hereinabovereferred to, the left hand radiating system can be operated at the lowerpressure and the right hand system at the higher pressure in a mannerexactly similar to that already described.

In some instances it may not be desirable to exhaust the flash tank Cinto the supply side of the lower pressure system, for example, wherethe difference in operating pressures between the two systems is notsufficient to re-vaporize a material quantityof the condensate in tankC. In such event, both cut-off valves '73 and 73' are closed, and thevalve '75 or '75 leading to the return main of the system operating atthe lower pressure is opened. The exhaust connection through pipe '70from flash tank C now leads directly to the return main of the lowerpressure system. The steam trap '76 or '76 will prevent the escape ofsteam from flash tank C and all of the condensate from this tank will bedrained out through float trap 67. Otherwise the operation is the sameas already described.

In case it is desired to operate both radiating systems at the samepressure, or the same degree of vacuum, both cut-off valves 58 and 58are opened and both valves 64 and 64 closed, so that both return mains Mand M drain directly into the exhausting mechanism. Either or both ofthe switches 87, 8'7 are closed to the right so that either or both ofthe differential controllers N and N are placed in control of the motorE of the exhausting mechanism. The entire heating system now operatesthe same as a single system, although it consists of two parallelsimultaneously operating branches. It may often be found desirable tooperate the system in the manner last described until most oi. the airhas been withdrawn from both branches of the system, and then establishthe desired difference in pressures between the two radiating systems byproper manipulation of the several valves and switches, as alreadydescribed.

It might be noted that in order to facilitate the disclosure in thediagrammatic views and show all of the piping system, many of the pipesare shown at different elevations from those actually occupied. Inactual installations, a great many of these pipes are grouped atpractically the same level and would appear one behind the other if soillustrated.

I claim:

1. In steam heating apparatus, a source of steam, two separate radiatingsystems, one operating at a lower pressure than the other, an exhaustingmechanism for maintaining a sub-atmospheric pressure in both systems,the exhausting mechanism being in direct communication with the systemoperating at the lower pressure, an exhaust connection between theoutlet side of the higher pressure system and the inlet side of thelower pressure system, a cutoff valve in this connection, and meansactuated by pressure variations in the higher pressure system foroperating the valve.

2. In steam heating apparatus, a source of steam, two separate radiatingsystems, one operating at a lower pressure than the other, an exhaustingmechanism for maintaining a sub-atmospheric pressure in both systems,the exhausting mechanism being in direct communication with the systemoperating at the lower pressure, an exhaust connection between theoutlet side of the higher pressure systemand the inlet side of the lowerpressure system, a cutoff valve in this connection, means actuated bypressure variations in the higher pressure system for operating thevalve, and means actuated by pressure variations in the lower pressuresystem for controlling the exhausting means. I

3. In steam heating apparatus, a source of steam, a heating systemcomprising a supply main leading from the source, a reducing valve forcontrolling the pressure in the supply main, a return main, a radiatorin communication with the supply main, connections including athermostatic trap between the radiator and the return main, and a flashtank into which the return main discharges condensate, a second heatingsystem, an exhausting mechanism for lowering the pressure in the secondheating system, and means automatically responsive to pressurevariations in the first heating system for intermittently placing anupper portion of the flash tank in communication with the supply side ofthe second heating system.

4. In steam heating apparatus, a source of steam, a heating systemcomprising a supply main leading from the source, a reducing valve forcontrolling the pressure in the supply main, 8. return main, a radiatorin communication with the supply main, connections including athermostatic trap between the radiator and the return main, and a flashtank into which the return main discharges condensate, a second heatingsystem, an exhausting mechanism, means controlling the exhaustingmechanism whereby it maintains a lower pressure in the second heatpipe,and a differential pressure controller connected with the supply andreturn mains of the first system and operating the valve.

5. In steam heating apparatus, a source of steam, a heating systemcomprising a radiator, a supply main, a return main, and a flash tankinto which the return main discharges condensate, an exhaustingmechanism, a second heating system, means controlling the exhaustingmechanism whereby it maintains a lower pressure in the second heatingsystem than the pressure in the return main of the first system and inthe flash tank, a pipe connection between the flash tank and the supplyside of the second heating system, a valve in this pipe, a diflerentialpressure controller for operating this valve, and control pipeconnections from the controller to the supply and return sides of theradiator.

6. In steam heating apparatus, a source of steam, a heating systemcomprising a radiator, a supply main, a return main, and a flash tankinto which the return main discharges condensate, a second heatingsystem, means for lowering the pressure in the second heating system,and means automatically responsive to pressure variations in the firstheating system for intermittently placing an upper portion of the flashtank in communication with the supply side of the second heating system.

7. In steam heating apparatus, a source of steam, two separate radiatingsystems, means including supply and return mains for maintaining steamfrom the source in each of these systems, a' reducing valve in eachsupply main whereby the steam is simultaneously maintained at adifierent sub-atmospheric pressure in each system, an exhaustingmechanism, a motor for operating the exhausting mechanism, adifferential pressure contrdller for the motor connected between thesupply and return sides of the system operating at the lower pressure, aflash tank, the return main of the lower pressure system leading to theexhausting mechanism and the return main of the higher pressure systemleading to the flash tank, a conduit connecting the flash tank with thesupply main of the lower pressure system, a valve in this conduit and adifierential pressure controller for this valve connected between thesupply and return sides 01' the higher pressure system.

8. In steam heating apparatus, a source of steam, two separate radiatingsystems, means including supply and return mains for maintaining steamfrom the source in each of these systems, a reducing valve in eachsupply main whereby the steam is simultaneously maintained at adifferent sub-atmospheric pressure in each system, an exhaustingmechanism, a motor for operating the exhausting mechanism, adifferential pressure controller for the motor connected between thesupply and return sides of the system operating at the lower pressure, aflash tank, the return main of the lower pressure system leading to theexhausting mechanism and the return mainof the higher pressure system'leading to the flash tank, a conduit leading from the flash tank andhaving branches connecting respectively with the supply and return mainsof the lower pressure system, cutofi valves in these branches, a controlvalve in the conduit, and a differential pressure controller for thislatter control valve connected between the supply and return sides ofthe higher pressure system.

9. In a steam system, a generator, a header leading therefrom, twoseparate radiating systems each system including a supply main leadingfrom the header, a reducing valve in the supply main, a radiatorcommunicating with the supply 7 main, a return main, dischargeconnections ineluding a thermostatic trap between the radiator and thereturn main, a differential pressure con troller, pressure control pipesconnecting the controller with the supply and return sides of the systemrespectively, and a switch operated by the controller in response tovariations in the pressure differential between the supply and returnsides of the system; a flash tank, an exhausting mechanism, valved pipeconnections for alternatively connecting each return main to dischargeinto either the flash tank or the exhausting mechanism, an exhaust pipeleading from the flash tank and having valved branches for alternativelyplacing the tank in communication with a portion of either radiatingsystem, an electrically operated cutoii valve in the exhaust pipe, andelectric circuits adapted to alternatively place each of thedifferential pressure controlled switches in control of, either theelectrically operated cutofi valve or the exhausting mechanism.

10. In a steam heating system, a generator, a header leading therefrom,two separate radiating systems each system including a supply mainleading from the header, a reducing valve in 'the supply main, aradiator communicating with the the controller with the supply andreturn sides 35' of the system respectively, and a switch operatedsupply main, a return main,.discharge connections including athermostatic trap between the by the controller in response tovariations in the pressure differential between the supply and returnsides of the system; a flashtank, an exhausting mechanism, valved pipeconnections for alternatively connecting each return main to dischargeinto either the flash tank or th'eexhausting mechanism, an exhaust .pipeleading,

from the flash tankand having valved for alternatively placing the tankin um; cation with a portion of either radiating system,

switch of the system operated at the lower 'lpressure'in control of theexhausting mechanismand,

the other switchin control of the electrically operated cut-ofi valve.

11. In a steam heating system, a generator, a header leading therefrom,two separate radiating systems each system including a supply-m leadingfrom the header, a reducing valve he 7 supply main, aradiator'communicating with the supply main, a return main, dischargeconnec tions including a thermostatic trap between the sure controller,pressure control pipes connect ing the controller with the supply andreturn sides of the system respectively, and a switch operated by thecontroller in response to variations in the pressure differentialbetween the supply and return sides of the system: a flash tank, anexhausting mechanism, valved pipe connections for alternativelyconnecting'each return main to discharge into either the flash tank orthe exhausting mechanism, an exhaust .pipe leading. from the flash tankand having valved branches for alternatively placing the tank incommunication with the supply main of either radiating system, anelectrically operated cut,- off valve in the exhaust pipe, and electriccircuits adapted to alternatively place each of the differential-pressure controlled switches in control of either theelectrically operated cut-oif valve or the exhausting mechanism.

12. In a steam heating system, a generator, a header leading therefrom,two separate radiating systems each system including a supply mainleading from the header, a reducing valve in the supply main, a radiatorcommunicating with the supply main, a return main, discharge connectionsincluding a thermostatic trap between the radiator and the return main,a differential pressure controller, pressure control pipes connectingthecontroller with the supply and return sides of the'systemrespectively, and a switch operated by the controller in response tovariations in the pressure differential between the supply and returnsides of the system; a flash tank, an exhausting mechanism, valved pipeconnections for alternatively connecting each re-: turn main todischarge into either the flash tank or the exhausting mechanism, anexhaust pipe leading from the flash tank and having valved branches foralternatively placing the tank in communication with either the supplyor return main of either radiating system, an electrically operatedcut-off valve in the exhaust pipe, and electric circuits adapted toalternatively place each of the differential-pressure controlledswitches in control of either the electrically operated cut-01f valve orthe exhausting mechanism.

-1 3. In 'a steam heating system, a generator, 2. header'leadingtherefrom, two separate radiating systems each system including a supplymain leading from the header, a reducing valve in the supply main, areturn main, discharge connections including a thermostatic trap between,the radiator and the return main, a differential pressure controller,pressure control pipes connecting the controller with the supply'a'ndreturn -"'ides of the system respectively, and a switch oprated, by, thecontroller in response to variations .m' the pressure differentialbetween the supply and-return sides of the system; a flash tank, anexhausting mechanism adapted to withdraw gases and condensate from thesystem and return condensate to the generator, a motor for drivingtheexhausting mechanism, valved pipe connections for alternativelyconnecting each return main-to discharge either into the flash tank orthe exhausting mechanism, an exhaust pipe leadvinglfl from-the flashtank and having valved iivranchesfor alternatively placing the tank incommunication-with a portion of either radiat- 3i? electrically operatedcut-oif valve ust pipe, electric circuits connecting supply main, aradiator, an' open pipe connection including a restricted inlet orificebetween the supply main and the radiator, a return main,

discharge connections including; a thermostatic trap between theradiator and the return main,

a differential pressure controller, pressure control pipes connectingthe controller with the supply and return sides of the systemrespectively,

, theswitches, the cut-off valve and the motor, and radiator and thereturn main, a differential pres-v 1 and a switch operated by thecontroller in re-. sponse tovariations inthe pressure difierentialbetweenvthe sup ly and 'retum sides oi. the system, a flashtank, an'exhausting. mechanism adapted to withdraw gases and condensate from thesystems andreturn'condensate tothe generator, a motor for drivingtheexhausting mech- I 'anism, valved pipe connectionsv for alternativelyconnecting each return main to discharge either into the flash tank orthe exhausting mechanism, anexhaust pipe leading-from the flash tank andhaving valved branches tor alternatively placing the tank incommunicationwith a portion of either radiating. system, an electricallyoperated cut-0E valve in the exhaust pipe, electric circuits supplymain, a radiator communicating with the supply main, a return main,discharge connections including a thermostatic trap between; the

radiator and'the return main, a difierential pressure controller,pressure control pipesfconnecting the controller with the-supply andreturn sides of the system respectively, and a switch j operated by thecontroller in response to variations in the pressure differentialbetween: the supply and return sides of the system; a flash tank, anexhausting mechanism adapted to withdraw gases and condensate from thesystems 7 and return condensate to the generator, a motor for drivingthe exhausting mechanism, valved pipe connections for alternativelyconnecting each return main to discharge either into the flash tank orthe exhausting mechanism, an ex-' haust pipe leading from the flash tankand having valved branches for alternatively'placing the tank incommunication with the supply main of either v radiating system, anelectrically operated cut-off valve in the exhaust pipe, electriccircuits connecting the switches, the cut-off valve and the motor, amaximum pressure regulator con- 'nected with the exhausting mechanismincluding a switch positioned in the motor-control circuit, anddouble-throw switches in said circuits where- ;byeach differentiallycontrolledswitch may be tern'atively placed in control of either theelec-. l't'rically'operated cut-ofl.v valve 'or' the motor.

,16. Iii a steam heating: system, Ta, source of steam, a heating systemcomprising'ia radiator,

asupply' main, a; return main and ;.,a' ;flash tank nto. which thereturn-{main discharges condensate,- and means for maintaining asub-.at-

mospheric pressure in the ma tank, revaporizing the condensate" therein;withdrawing the re sultant steam'and'iutilizing this-steam'tor heat-.ing purposes, said means comprising arrexhaust ingapparatus, ,a conduit,connection including a secondheating system between the flash-tank andexhausing apparatus, a valve in this connection at the outlet of theflash-tank, and means automatically responsive to pressure variations inthe first heating system for opening and clos ing the valve.

DAVID N. CROSTHWAI'I, JR.

